Abstract:

The objectives in this research were to assess whether Klebsiella planticola
SDF20 could survive in soil and result in ecological effects to soil foodweb
organisms and plant growth. Four experiments were conducted using soil
microcosms. Klebsiella planticola SDF20 has been genetically engineered to
produce ethanol from agricultural waste for use in alternative fuels.
Theoretically, after ethanol is removed from fermentors, the remaining residue
that includes SDF20 would be spread onto crop fields as organic amendments.
The parent strain SDF15 and genetically engineered strain SDF20 were added
to sandy and clay soils with varying organic matter content. Alterations to soil
foodweb organisms and plant growth were assessed using direct methods.
These alterations were considered to be ecological effects if changes in nutrient
cycling processes and plant growth would result. Ethanol produced by SDF20
was detected in the headspace of microcosms that demonstrated that SDF20
can survive and express its novel function in high organic matter clay soil. Soil
containing higher organic matter and higher clay content may have increased
the survival of SDF20 due to less competition with indigenous microbiota for
substrates and protection from bacterial predators in clay soil with smaller pore
sizes, thereby allowing SDF20 to produce a detectable concentration of ethanol.
Significant changes to soil foodweb organisms were not detected using this soil
type. However, significant increases in soil nematodes and significant
decreases in vescular-arbuscular mycorrhizal colonization of plant roots were
detected after the addition of SDF20 to low organic matter clay, low organic
matter sandy and high organic matter sandy soils. Significant changes in soil
foodweb organisms associated with SDF20 occurred only when living plant roots
were present. This indicated the importance of having biotic interactions in test
systems to elucidate ecological effects. The effects associated with SDF20
varied with the chemical, physical and biological properties of soils and indicated
the importance of assessing the release of genetically engineered
microorganisms on a case by case basis.